The invention relates to a holding furnace with a metering device for molten baths, in particular for metering light molten bath during diecasting.
DE-OS 2022989 describes an automated metering system for molten metal intended to precisely meter molten baths. The automated metering system is part of a holding furnace, which is charged with a molten bath by way of a loading flap. The melt to be metered is discharged through a discharge tube, which is provided with two measuring electrodes. If the melt is to be metered, the furnace is pressurized with compressed air, and the melt rises in the discharge tube until it reaches the measuring electrodes, so that a pulse is emitted to a controller. The set quantity of molten bath flows out of the discharge tube. The furnace is then ventilated via a timer, and the outflow of molten bath is abruptly terminated. However, the accuracy required for present-day conditions is inadequate, and the formation of slag is disadvantageous.
Also known is another device for casting molten metal according to DE-A-19821650, which has a metering container connected in terms of flow with the hearth of a holding furnace by means of a sealable opening. The metering container can be evacuated by exposure to compressed gas via a riser, wherein the opening is located in the bottom of the metering container, and can be sealed from inside by means of a valve gate on a valve rod. The opening is semicircular or conical. The valve rod and valve gate are arranged inside the metering container. The fill level in the metering container is determined by means of a fill level sensor in the metering container.
At the beginning of a metering process, melt flows of its own accord into the metering container via the open floor valve up to a predetermined working fill level. After reaching the desired level, the opening of the floor valve is closed by lowering and turning the valve gate. Backflow in the riser is possible during renewed filling of the metering container. Undesired oxides may deposit in the riser as a result.
DK 199800409 shows a similar solution, wherein the holding furnace is height-adjustable. The height is adjusted by means of a scissor-type jack.
DE-A-10034946 discloses a reciprocating pump, whose valve unit is comprised of an inlet and outlet valve combination. Such a valve is geometrically captive, and hence cannot be disassembled without a complicated process for cleaning the reciprocating pump.